The present invention relates to a method for feeding a carding group with pneumatic conveying system, in which the feeding arrangement supplies a plurality of feed chutes, and apparatus for implementing the method.
With a known method, a transport fan blows fiber flakes through a conveying duct in feed chutes of carding feeders. At each location where a feed is connected to the conveying duct, there is a rectangular opening in the conveying duct; the width of this opening equals the width of the feed chute. The fiber flakes are conveyed through the conveying duct in an irregular manner, i.e., with different volumes per unit time. The fiber flakes drop from the conveying duct through the opening in the feed chute and are deposited there vertically and horizontally distributed at random. For example, if the feed chute is 1 m wide, a larger portion may drop on one end into the opening, and a smaller portion may drop on the other end into the opening so that the accumulation in the feed chute is of varying height. As a result, the flake accumulation across the width exerts a varying pressure on the take-up roller so that a fleece of varying thickness (density) is pulled from the feed chute. In addition, the flakes do not drop in equal quantities into the feed chute so that the flakes accumulation in the feed chute has zones of larger or smaller density; frequently there are areas which have no flakes whatever. With irregular accumulation, under the influence of the excess pressure prevailing in the conveying duct, there may develop an air flow from the top to the bottom which concentrates on the zones of lower density and hence vertically compresses the flakes lying on top of one another. However, this merely compresses the zones of larger and smaller density vertically. The varying height distribution of the flake accumulation is not remedied. However, a uniform flake distribution both within the flake accumulation and over the height of the flakes deposited on top of one another is a decisive factor for the uniformity of the fleece delivered to the cards and thus of the card band.
It is, therefore, an object of the present invention to provide a method of the above type which is free from these disadvantages, and in a simple manner permits uniformity of flake accumulation across the entire cross section of the feed chute.
Another object of the present invention is to provide an arrangement, as described, which is substantially simple in construction and may be economically fabricated.
A further object of the present invention is to provide an arrangement, as described, which may be readily maintained in service, and which has a substantially long operating life.